Heat exchanger

ABSTRACT

A heat exchanger of the construction wherein a plurality of tubes for passing dust-containing gas therethrough are arranged substantially in parallel with a rotating shaft, a passage for a fluid to be heated is provided among the cluster of the tubes, scraper members are disposed within the individual tubes, one for each, and means are provided for driving the shaft, so that the rotation of the shaft enables the scraper members to slide down gravitationally within the revolving tubes to remove the dust from the inner wall surfaces thereof.

United States Patent 1 Takahashi 1 1 Oct. 2, 1973 HEAT EXCHANGER Inventor: Masao Takahashi, Tokyo, Japan [73] Assignee: Japan Engineering and Trading Company Limited, Tokyo, Japan 221 Filed: Dec. 29, 1971 211 Appl. No.: 213,381

[52] US. Cl 165/95, 34/142, 259/82 [51] Int. Cl. F28g 3/00 [58] Field of Search 154/5, 10, 92,

[56] References Cited UNITED STATES PATENTS 3,208,512 9/1965 Kalmbach et al /92 2,601,972 7/1952 Rose 165/95 2,233,066 2/l94l Watson 11 165/95 Primary Examiner-Charles J. Myhre Assistant Examiner-Theophil W. Streule, Jr.

Attorney-George B. Oujevolk [57] ABSTRACT A heat exchanger of the construction wherein a plurality of tubes for passing dust-containing gas therethrough are arranged substantially in parallel with a r0- tating shaft, a passage for a fluid to be heated is provided among the cluster of the tubes, scraper members are disposed within the individual tubes, one for each, and means are provided for driving the shaft, so that the rotation of the shaft enables the scraper members to slide down gravitationally within the revolving tubes to remove the dust from the inner wall surfaces thereof.

5 Claims, 4 Drawing Figures United States Patent 1 Takahashi Oct. 2, 1973 PATENIEUBBT e SHEET 10F 2 MASAO T/IKAIXASHI I NVEN TOR.

GEORGE B. OUJEVOLK ATTORNEY- PATENIEDW 21w SHEET 2 BF 2 FIG.4

MASAO T A Kl. HA 5 HI mvuwoRf BY GEORGE B. OUJEVOLK ATTORNEY HEAT EXCHANGER This invention relates to improvements of a heat exchanger of the type wherein gases resulting from combustion are led through tubes so that the heat can be transferred to another substance outside the tubes.

Usually the waste gases from furnaces are hot and dusty. The dust in the form of minute particles contains tar and pitch and is therefore sticky. Consequently, in a heat exchanger of the type designed to pass such flue gas through tubes for transfer of the heat to a substance outside, the dust deposits on the inner wall surface of the tubes and reduces the heat transfer efficiency, thus making it impossible to operate the exchanger for a long time. For this reason the heat transfer surfaces of the tubes must be cleaned at regular intervals.

In view of the foregoing, the present invention has for its object the provision of a heat exchanger which can automatically remove dust from the tubes through which flue gas passes so as to maintain its maximum heat-exchange efficiency.

In essence the invention resides in a heat exchanger characterized in that a plurality of tubes through which hot (flue) gas passes are arranged in parallel to a shaft, scraper members are inserted into the tubes, one for each, and the shaft is driven for rotation so that the scraper members can gravitationally slide down along the inner wall surfaces of the individual tubes to prevent deposition of dust on the inner wall surfaces of said tubes.

The present invention will be better understood from the following detailed description taken in conjunction with the accompanying drawings showing preferred embodiments thereof.

IN THE DRAWINGS:

FIGS. l-I and 1-" are schematic views of a heat exchanger embodying the invention, FIG. l-I being a vertical sectional view and FIG. lII a sectional view taken on the line X-X of FIG. l-I, both showing tubes 14 without scraper members inserted therein:

FIGS. 2-I and 2-1] show a scraper member for each heat-exchange tube; FIG. 2-I being a longitudinal sectional view and FIG. 2- a cross sectional view;

FIGS. 3-I and 3- show another form of scraper member for the heat-exchange tube, FIG. 3-I being a longitudinal sectional view and FIG. 3-" a cross sectional view; and

FIG. 4 is a view illustrative of the function of the scraper member within the heat-exchange tube of FIG. 2.

Referring to FIG. 1, a shell 1 is shown placed on a bed 2. It is hollow and substantially cylindrical in cross section. It has an inlet 4 and an outlet 3 for a lowtemperature gas in its upper portion and a passage 5 for the gas in its lower portion. Through the center of the shell 1 is rotatably extended a hollow shaft 6 having a solid shaft 7, which is journaled at both ends in bearings 8, 9 supported on the bed 2. Near one end of the shaft 6 is fixedly mounted a sprocket 10, which is connected, though not shown, to a motor through a chain so that the rotational power can be transmitted to the shaft 6. Partitions l1, l2, 13 are located within the shell 1 and secured onto the hollow shaft 6. Each partition is a circular plate, through which a number of heat-exchange tubes 14 extend, all in parallel with the shaft 7. Adjacent the front ends of the tubes 14, or at the left of the tubes as viewed in FIG. 1-I, there is formed a hot gasdistributing chamber 15 which is formed with an inlet 16 for a hot, dust-containing gasin its upper portion. At the rear ends of the tubes, at the right thereof, is defined a collecting chamber 17, which has a gas outlet 18 in its upper portion. These two chambers are communicated to each other through the cluster of tubes 14 but are kept stationary and unmovable with the tubes. They are completely insulated, from the shell I. As shown in FIG. 2, a scraper member 19 is inserted into each of the tubes 14. The scraper members 19 to be used may be in the form of flat bars, chains, coarse sands, or steel strips. Where coarse sands or steel strips are to be used, inwardly extended flanges or end pieces must be provided at the both ends of the tubes to keep the inserts from dropping out of the tubes. In the embodiment shown, flat steel bars are used.

Each scraper member is longer than the tube and has holes 20 at the both ends, and a pin (not shown) longer than the inside diameter of the tube is inserted crosswise through each hole to prevent the scraper member from coming off from the tube M. The scraper members 19 are narrow enough to slide down and maintain their original positions within revolving tubes. (See FIG. 2)

In the heat exchanger shown, hot gas is introduced into the distributing chamber 15 through the inlet 16. It is then led through the cluster of tubes 14 and the collecting chamber 17 and finally discharged from the outlet 18. On the other hand, the gas to be cooled enters the shell 1 via the inlet 4, and passes downward through the space among the portions of the tubes 14 between the partitions l2 and 13, while being heated through contact with the hot outer walls of the tubes. By way of the lower passage 5 of the shell the heated gas flows upward through the space among the tube portions between the partitions l1 and 12, thus gaining additional heat from the tubes. The gas heated in this way leaves the outlet 3 for a destination where it is required. During the course of heat exchange above described, the cluster of tubes 14 revolves around the common shaft so that the gas being heated is mixed well for uniform heat transfer. Meanwhile, the scraper members disposed in the tubes 14 remain in their original positions as they slide down by gravity within the revolving tubes, thereby scraping off the dust from the inner wall surfaces of the tubes. The inside of each tube is thus kept clean. Consequently the dust is forced with the flue gas toward the outlet 18 and thence to a dust collector not shown for disposal.

The manner in which dust is scraped off by a scraper member 19 will now be described in more detail with reference to FIG. 4. The tube 14 is always in the same circumferential position with respect to the center 0 of the rotating shaft. This means that one rotation of the shaft causes one revolution of the tube 14 therearound, moving it for example from the point A to the points B, C, D and back to the original position while, at the same time, allowing the tube itself to make one complete turn.

If it is assumed that the lower edge of the scraper is at the point P of the inner wall of the tube 14 as in the position A, the movement of the tube 14 to the positon B with the rotation of the shaft would cause a quarter turn of the tube itself, but the scraper member 19 would gravitationally slide down along the inner wall surface to maintain its original position as in the position A. In the meantime the scraper member with its lower edge would scrape off the dust from the inner wall surface. As the tube makes one revolution through the positions C, D and A, the scraper member 14 would complete scraping of the entire surface of the inner wall.

Another embodiment of the invention, as illustrated in FIG. 3, uses chain scraper members 21 inserted through heat exchange tubes 14.. Each length of chain is provided with stopper pins 22 at the both ends which prevent the chain from slipping out of the tube 14'. With this arrangement, the revolution of the tubes 14 causes the chain scraper members 21 therein to keep sliding contact with the inner wall surfaces of the tubes and thereby scrape off the dust from the entire surfaces.

As described above, the heat exchanger according to this invention is equipped with scraper members inside the heat-exchange tubes arranged in parallel with a rotating shaft in such a manner that the rotation of the shaft enables the scraper members to slide down by gravity within the revolving tubes and scrape off the dust from the inner wall surfaces in an automatic way. The exchanger thus saves the labor for cleaning the tubes, maintains its maximum heat-exchanging efficiency at all times, and proves thermally economical.

What is claimed is:

l. A heat exchanger of the construction wherein a plurality of tubes for passing dust-containing gas therethrough are arranged substantially in parallel with a rotating shaft, a passage for a fluid to be heated is provded among the cluster of the tubes, scraper members are disposed within the individual tubes, one for each, and means are provided for driving the shaft, so that the rotation of the shaft enables the scraper members to slide down gravitationally within the revolving tubes to remove the dust from the inner wall surfaces thereof.

2. A heat exchanger comprising at least two partition plates fixedly mounted in a spaced relationship on a common rotating shaft, a plurality of tubes held by said partition plates substantially in parallel with the rotating shaft, a stationary shell which houses the cluster of tubes revolvably and has an inlet and an outlet, a passage for a fluid to be heated defined by the shell, partition plates, and cluster of tubes, a distributing chamber for the hot gas for heat exchange which is provided adjacent the inlets of the tubes in communication therewith, a collecting chamber provided adjacent the outlets of the tubes in communication therewith, and scraper members disposed within the individual tubes, one for each.

3. A heat'exchanger according to claim 1 wherein the scraper members are elongate metal bars extended beyond the entire length of the individual tubes.

4. A heat exchanger according to claim 1 wherein the scraper members are chains.

5. A heat exchanger according to claim 1 wherein the scraper members are a plurality of flat steel bars. 

1. A heat exchanger of the construction wherein a plurality of tubes for passing dust-containing gas therethrough are arranged substantially in parallel with a rotating shaft, a passage for a fluid to be heated is provded among the cluster of the tubes, scraper members are disposed within the individual tubes, one for each, and means are provided for driving the shaft, so that the rotation of the shaft enables the scraper members to slide down gravitationally within the revolving tubes to remove the dust from the inner wall surfaces thereof.
 2. A heat exchanger comprising at least two partition plates fixedly mounted in a spaced relationship on a common rotating shaft, a plurality of tubes held by said partition plates substantially in parallel with the rotating shaft, a stationary shell which houses the cluster of tubes revolvably and has an inlet and an outlet, a passage for a fluid to be heated defined by the shell, partition plates, and cluster of tubes, a distributing chamber for the hot gas for heat exchange which is provided adjacent the inlets of the tubes in communication therewith, a collecting chamber provided adjacent the outlets of the tubes in communication therewith, and scraper members disposed within the individual tubes, one for each.
 3. A heat exchanger according to claim 1 wherein the scraper members are elongate metal bars extended beyond the entire length of the individual tubes.
 4. A heat exchanger according to claim 1 wherein the scraper members are chains.
 5. A heat exchanger according to claim 1 wherein the scraper members are a plurality of flat steel bars. 